Patent Application
20120037262
People at elevated positions above a floor or other relatively lower surface are at risk of falling and injury. For example, workers and other personnel who have occupations that require them to be at elevated positions, such as on scaffolding, are at risk of falling and injury. Safety harnesses are often worn to stop a person's fall and prevent or reduce injury.
Safety harnesses typically have a harness portion worn by the user and a tether or lanyard extending from the harness portion. The lanyard connects the harness portion to a secure structure. If a person falls from the elevated position the safety harness stops the person's fall when the lanyard is straightened.
A load limiter on a seat belt system can be worn to secure the occupant of a vehicle in the event of a sudden stop or collision to reduce the risk of injury. If a person is subjected to inertia due to a vehicle's sudden stop, the load limiter limits the person's forward movement when the load limiter is straightened.
Retractable lanyard devices are used in some fall protection applications, and retractable load limiter devices are used in some seat belt systems. Retractable lanyard devices are typically comprised of a flat webbing that is capable of being received within a retractor. Existing retractable lanyard devices have a mechanical device in the retractor to stop the fall (by preventing the webbing from advancing further out of the webbing) or to dissipate energy (by deforming metal). With typical retractable lanyards devices, however, the person's movement is stopped rather abruptly and the person is subjected to the shock force of the abrupt stop. Moreover, existing retractable lanyard devices are bulky, heavy, and costly.
Lanyards that attempt to absorb the shock of a person's fall are known. Such lanyards, however, have bunched, accordion-type sections that lengthen as energy is absorbed. These bunched sections prevent the use of an energy absorbing webbing in a retractor, since a retractor requires the use of a flat webbing. Thus, a need exists for a retractable lanyard that absorbs energy.
Certain embodiments of the invention generally pertain to energy absorbing webbings and lanyards, and methods of making them. More specifically, some embodiments of the invention pertain to an energy absorbing webbing that is generally flat and therefore capable of being received within a retractor.
Certain embodiments of the invention provide webbings 10 that are suitable for use in retractors, such as retractor 12 shown in
As shown in
Elongation yarns 14 are highly extensible yarns and significantly stretch when placed under a tensile load. The elongation yarns 14 are one example of an energy absorbing member of the webbing 10. In one embodiment, the elongation yarns 14 are partially oriented yarns (POY) made of polymer materials such as polyester, but the elongation yarns 14 can be made from one or more suitable materials having high elongation properties and the ability to shrink in length substantially more than the ground yarns, such as during heat treatment. In some embodiments, each of the elongation yarns has a linear density of between approximately 300 denier and approximately 5,580 denier.
The elongation yarns 14 have an elongation property that allows the elongation yarns 14 to stretch significantly under a predetermined tensile force. The elongation yarns 14 have this elongation property even after they are subjected to a heat treatment process. When the webbing 10 is placed under tensile load, the elongation yarns 14 stretch under tension and absorb some of the force or energy applied to the webbing 10. Accordingly, the elongation yarns 14 are a shock and energy absorbing member that provides a shock and energy absorbing feature.
In some embodiments, lateral yarns 18 (also referred to as “weft” or “pick” yarns) are woven in a weft direction across the webbing 10 to secure the elongation yarns 14 and the ground yarns 16 laterally across the webbing 10. In some embodiments, the lateral yarns 18 are approximately 1,000 denier polyester yarns. In other embodiments, the lateral yarns 18 are industrial filament polyester, nylon, Nomex, Kevlar, or any other suitable yarn.
Important properties of the elongation yarns 14, which serve as the energy absorbing member, include some or all of high elongation, high shrinkage, and high shrink-force (the force produced during the shrinkage). The elongation yarns 14 should have sufficiently high elongation and load bearing properties under load to absorb the load energy so as to reduce shock to a person or other body in a sudden deceleration state such as that caused by a fall from a building, a parachute deploying, or an impact due to an automobile or aircraft accident. In some embodiments, the webbings are adapted for use where dissipation of kinetic energy is required.
Webbings of the present invention may be foamed on any desired programmable loom, such as a needle loom. As described above, the webbing 10 includes elongation yarns 14, ground yarns 16, and lateral yarns 18.
The draw-in diagram of
In one embodiment, the webbing 10 is a 4 foot by 1 and ⅜ inch nylon structure formed from approximately 248 Kevlar ground yarns (the ground yarns having a linear density of approximately 1,500 denier) and 90 elongation yarns (the elongation yarns being partially oriented yarns with a linear density of approximately 5580 denier).
In some embodiments, one end of the webbing 10 is attached to a hardware component, such as a clip 11, metal clasp, harness, or seatbelt component, while the other end of the webbing 10 is situated within a retractor 12 (shown in
In some embodiments, the webbing 10 is used as a deceleration device, to secure the occupant of a vehicle against harmful movement that may result from a sudden stop, or in any other application where rapid human or other body deceleration may occur. When using the webbing as a fall protection device, one end of the webbing 10 is securely attached to a safety harness worn by a user. The opposite end of the webbing 10 is securely attached to a fixed structure. If the user falls, the webbing 10 stops the person's fall and reduces the shock felt by the person as the user is brought to a controlled deceleration. As the person falls, the webbing 10 straightens and the load of the user is applied to the webbing 10. The elongation yarns 14 stretch and absorb the force of the load applied to the webbing 10. As the elongation yarns 14 stretch, the webbing 10 elongates. In the embodiments where the webbing is used with a retractor, once the webbing 10 has retracted from the retractor 12, the webbing 10 stops the person from falling any farther. The shock of stopping the fall that would otherwise be felt by the falling person is reduced or cushioned by the energy-absorbing elongation yarns 14.
Also provided is a process of manufacturing a generally flat energy absorbing woven webbing, such as webbing 10. In one embodiment, webbing 10 is subjected to heat treatment to shrink the length of the elongation yarns 14. When the webbing 10 is subjected to heat treatment, the elongation yarns 14 shrink in length while the ground yarns 16 do not, resulting in a greater weave-in of the elongation yarns 14 than the weave-in of the ground yarns 16, where weave-in refers to the percentage difference in the length of the yarn before weaving and the length of the webbing after weaving. In some embodiments, the ground yarns 16 and the elongation yarns 14 both start with an about 6% weave-in, such that the length of the elongation yarns 14 and the ground yarns 16 are approximately 6% greater than the length of the webbing 10. In one embodiment, after the webbing 10 is subjected to heat treatment, the length of the elongation yarns 14 and the length of the webbing 10 shrink by approximately 20%, while the length of the ground yarns 16 does not shrink. Thus, in this embodiment, the elongation yarns 14 will remain at around 6% weave-in while the ground yarns will have around 26% weave-in. In this way, the relative lengths of the elongation yarns 14 and the ground yarns 16 are automatically adjusted upon heat treatment. In one embodiment, the webbing 10 is heat treated in a manner so that shrinkage of the elongation yarns 14 is controlled.
For example, as illustrated in
In one embodiment, the webbing 10 is fed through the first set of rollers 22 to the heat source 24, and out through the second set of rollers 20. As shown in
In one embodiment, the speed at which the webbing 10 is fed through the first set of rollers 22 is greater than the speed at which the webbing 10 is fed through the second set of rollers 20. For example, in one embodiment, the feed speed associated with the first set of rollers 22 is approximately 10 yards per minute, while the feed speed associated with the second set of rollers 20 is approximately 8 yards per minute, for a feed ratio of 20%. Since the webbing 10 is exiting the heat source 24 at a speed that is 20% slower than the speed at which it entered the heat source 24, the webbing 10 is subjected to an over feed ratio of 20% during heat treatment by the heat source 24. In this way, the elongation yarns 14 will remain in tension between the first set of rollers and the second set of rollers and will be allowed to shrink approximately 20%, while the other materials (such as the ground yarns 16) are gathered by the forces of the elongation yarn shrinkage, which results in a greater than 20% weave-in and a length reduction of 20%. Because the elongation yarns 14 shrink when subjected to heat, while the ground yarns 16 do not have more than minimal shrinkage, the heat treatment process adjusts the relative length of the elongation yarns and the ground yarns. In some embodiments, the webbing 10 is subjected to approximately less than 5 minutes of heat treatment at a temperature of about 220° F.
The amount of elongation yarns 14 in the webbing 10 may be varied to adjust the forces required to elongate the webbing 10. Similarly the shrinkage of the elongation yarns 14 in the webbing 10 may be varied to adjust the elongated distance, or the relative difference in length between the elongation yarns 14 and the ground yarns 16 of the webbing 10. As described above, the difference in length between the two sets of yarns is caused by the difference in weave-in of the yarns. Similarly, the feed ratios between the first set of rollers 20 and the second set of rollers 22 may be varied to adjust the forces required to elongate the webbing 10 and the elongation distance of the webbing 10. Finally, the duration and amount of heat applied to the webbing 10 also may be varied to adjust the forces required to elongate the webbing 10 and the elongation distance of the webbing 10. This allows the properties of the webbing 10 to be tailored to the needs of the user and/or the application.
Various heat treating processes can be used to shrink the elongation yarns 14. For example, a continuous oven may be used in an in-line, continuous heating process. The webbing 10 may be continuously woven and fed into the continuous oven for heat treatment. Another example of heat treatment is a batch process in which individual webbings are heat treated.
In one embodiment, a webbing 10 is designed to stop a falling person within 3.5 feet, which is in compliance with 29 C.F.R. 1926.104(d) (2008). In this embodiment, the webbing 10 has a finished, ready-for-use length of about 6 feet. Prior to the heat treatment, the elongation yarns 14 and the ground yarns have a length of approximately 9.5 feet. After heat treatment, the elongation yarns 14 have a reduced length of about 6 feet and the ground yarns 16 essentially retains their length of 9.5 feet. During use of the webbing 10, the elongation yarns 14 will stretch from about 6 feet to about 9.5 feet. When the webbing 10 reaches the maximum 9.5 feet length, the webbing 10 stops the person's fall. The elongation yarns 14 absorb the energy of the fall and reduce the abrupt shock to the person when the webbing 10 stops the fall. In other embodiments, the webbing has a finished, ready-to-use length of about 4 feet. In one embodiment having a ready-to-use length of about 4 feet, the percentage of elongation yarns to ground yarns is approximately the same, however, the ratio of ground yarns to elongation yarns may vary depending on the application. For example, more ground yarns to elongation yarns may be required for higher strength applications, and more elongation yarns to ground yarns may be required when a greater deployment force is required.
In another embodiment of the present invention, a webbing has lengths of the elongation yarns and the ground yarns to stop a falling person within about 11.75 feet. The webbings, however, can be made in any desired length according to the present invention.
The webbings of the present invention can be made of any suitable materials including, but not limited to, synthetic material yarns woven to form the fabric structure.
Various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.
